The present invention relates to a technique for generating audio data for loop reproduction on the basis of a sequence of performance data, such as MIDI data.
Heretofore, there has been known a technique for creating an audio file capable of reproducing tones similar to tones reproduced on the basis of performance data, such as MIDI data, by converting the performance data into audio data (waveform data) and storing the converted audio data (see, for example, Japanese Patent Application Laid-open Publication No. 2000-338979 and U.S. Pat. No. 6,535,772B1 corresponding thereto). With such an audio file creation technique, it is possible to create, for example via a personal computer, audio data on the basis of performance data and allow the created audio data to be used on a desired audio player. Thus, using such a created audio data file, even an audio player capable of reproducing only audio data, for example, can reproduce tones based on the performance data, such as MIDI data, that by nature could not be reproduced on the audio player. Note that the term tones” as used in this specification is not limited to musical sound sounds but embraces voices and other types of sounds.
Further, recently, it has become possible to install in advance a music application software program, configured to implement predetermined music functions, in electronic equipment, such as a slate-type personal computer, smart phone or the like, so that the music application can operate on the electronic equipment. Thus, a user can enjoy using the electronic equipment not only as a mere reproduction apparatus (audio player) capable of reproducing tones but also as an electronic music apparatus having various music functions corresponding to the music application. One example of such a music application is known which is configured to allow a user to create a phrase performance as desired by repetitively reproducing (loop-reproducing) an audio file (commonly called a “tone template”) comprising one or more prestored measures selected and arranged time-serially by the user. The aforementioned audio file creation technique can be used meaningfully in relation to such a music application. For example, using the aforementioned audio file creation technique, a sequence of performance data constituting a music piece or phrase is reproduced, and audio data obtained through the reproduction of the sequence of performance data are stored into a suitable memory as an audio file of the music piece or phrase. In the aforementioned music application, a user selects, as a looping portion, the stored audio data of a part of the music piece or whole or part of the phrase and causes the selected looping portion to be reproduced in a looped fashion or loop-reproduced.
For example, in a case where tones of a performance pattern having a four-measure length are to be reproduced repetitively (i.e., loop-reproduced) on the basis of a sequence of performance data of certain four measures, the tones of the four-measure performance pattern are audibly generated generally in such a manner that, at the time of reproduction of a first cycle of the loop, there occurs a silent state at the beginning and then audible tone generation starts with a first tone of the first measure and continues till the fourth measure. Then, at the time of reproduction of second and subsequent cycles of the loop, the tones of the same four-measure performance pattern are audibly generated repetitively; however, it is likely that there occurs no silent state at the beginning of the loop due to presence of a release portion or reverberation portion of a tone generated in the preceding cycle. Because, the tones based on the performance data are allocated to individual channels and audible generation of the tones is controlled independently among the tones, and thus, a tone whose audible generation has been started in a certain cycle of the loop (i.e., in a certain loop cycle) would get into a time region corresponding to the next loop cycle and continue sounding as a residual tone portion in that time region, regardless of the end of that cycle, depending on a control state of the release, reverberation or the like of the tone. Such mixing-in of the residual tone portion from the certain cycle to the next cycle during the loop-reproduction of the performance data would not necessarily give an unnatural feeling to a listener; rather, it would give a natural feeling to the listener.
However, with the prior art audio file creation technique, the aforementioned particular conditions involved in loop reproduction of a sequence of performance data are not taken into account. For example, the prior art audio file creation technique merely reproduces a sequence of performance data constituting a music piece or phrase and then stores audio data, obtained through the reproduction of the sequence of performance data, into a suitable memory as an audio file of the music piece or phrase. Thus, in a case where such audio data of a part of a music piece or the whole or a part of a phrase are selected as a looping portion and loop-reproduced, the selected looping portion is merely reproduced repetitively. Therefore, in each loop cycle, a residual tone portion from a preceding loop cycle would not mix into a beginning region of the loop cycle, so that an unnatural feeling would be given to a listener.
If the audio file created on the basis of the performance data according to the prior art technique is reproduced repetitively as above, tones that have not be influenced by a release portion or reverberation portion of a tone generated in the preceding cycle are generated per repetition, and thus, there would arise a problem that a user can't help but have an uncomfortable feeling. However, no technique for solving such a problem has been proposed yet.